1. Field of the Invention
The present invention relates to a communication system for transmitting and receiving enhanced text messages with commercial FM radio broadcasts; and more particularly, to a radio communication system wherein the enhanced text messages are displayed on the face of a radio receiver.
2. Description of the Prior Art
The Radio Data Systems (RDS) was developed in Germany in the 1980s as an outgrowth of a traffic alerting system. It is widespread throughout Europe, and was introduced into the US in 1993 where it is known as Radio Broadcast Data System (RBDS). In 1997, numerous automakers introduced RDS radios in the US. RDS uses a low data rate digital subcarrier at 57 kHz to transmit data such as a station""s call letters or program type (Jazz, etc.) along with the main radio signal. The data rate is 1187.5 bits per second, equivalent to a 1200 baud modem, although after overhead and mandatory protocol elements are accounted for the remaining data rate available to applications is about 300 bits per second. There is also a provision for sending 32 or 64 character text messages, referred to as xe2x80x9cRadio Textxe2x80x9d. The data is typically displayed on a small monochrome text screen mounted on the radio""s face. Most commonly, this screen is 8 characters long, and Radio Text messages are scrolled across the screen to present the entire message.
The RBDS standard is created and published by the National Radio Systems Committee (NRSC), formed jointly by the National Association of Broadcasters (NAB) and the Consumer Electronics Manufacturers Association (CEMA), a division of the Electronics Industry Association (EIA). The RBDS standard is a derivative of the RDS standard published by the European Broadcasting Union, headquartered in Geneva, Switzerland, as CENELEC EN50067.
The RDS data stream consists of 16-bit blocks called A, B, C, and D, which are transmitted sequentially in endless repetition. Each block carries a specific data type, which is defined by the RDS protocol. The A block always carries the radio station ID, B-blocks contain control information, the C block carries either station ID or data, and the D-blocks contain data. Each specific arrangement of A, B, C, and D blocks is called a group, of which there are 32 types, divided into 16 type A groups, and 16 type B groups. The RDS and RBDS standards define specific meanings or applications for several of these groups, while several groups remain unused and undefined. The first four bits of the B block defines to the group number of the possible 16 groups within a group type, and the next bit defines if it is a group type A (bit 5=0) or a group of type B (bit 5=1). Group types are referred to with the notation 0A, 0B through 15A, 15B. The distinguishing character of group type B is that the station ID from the A-Block is duplicated in the C-block of the group, making this slot unavailable for data. In the US, the station ID serves no purpose.
The Group Type determines the application, and thereby the definition of all the variable bits in the B-Block. The Group Types and applications of primary interest to broadcasters in the US include: 0A, Alternate Frequency and Program Service Name (Slogan); 2A and 2B, Radio Text; 10A, Program Type Name (PTYN); and 0B and 15A, Program Service Name (Slogan).
Only one or two applications can be defined by an individual Group Type, that matter being determined by whether the C- and D-Blocks will be used for the same application, or whether the C-Block will carry one application while the D-Block will carry another. As an example, the Group 0A has two applications, one in which the C-Block carries Alternate Frequency information, and one in which the D-block carries Program Service information (also called Slogan).
Two individual bits in the B block are used for highway traffic announcement related indicators (the TP bit, and the TA bit). The TP bit assignment is common to all group types, while the TA bit assignment is only defined in three of the group types. In the prior art, the B block was configured as described in FIG. 2.
One deficiency of the present arrangement is that radio stations can identify themselves as one, but only one, of the 32 categories of Program Types using the PTY bits as listed in TABLE I below. Thus a radio station could define itself as a Rock station, and a listener using an RDS receiver designed to scan for stations by format would be able to find this station. If during a News, Weather, or Sports announcement the station wished to be found by scanning, they could change their PTY to one of News, Weather, or Sports. If the station had selected News, and a listener were scanning at that moment for News, the station would be found. However, once the station changes its PTY from Rock to News, other receivers searching for Rock stations will not discover it until it changes back. Thus, a station can use RDS to identify itself by any one of the available Program Types, specifying a music format (Rock, Classical, Jazz, etc.), or a non-musical program format (News, Weather, or Sports), but only one at a time; and if the station is classified by anything other than what a listener is scanning for, it won""t be found.
A similar deficiency relates to the Traffic Program (TP) identifier bit. According to the standards, a radio station may turn on the TP bit to indicate that the station does provide traffic announcements sometime during the day. Obviously, this fact by itself is not very meaningful to listeners interested in hearing a traffic report. The TP bit is associated with a Traffic Announcement (TA) bit (bit 4) for group types 0A, 0B, and 15B. The meanings of TP/TA bit combinations according to the RBDS standard are described in TABLE II.
In groups such as 1A and 1B where bit 4 is not defined as TA, an explanation of how to interpret the TP bit is not provided in the standard. The way the TP/TA scheme is designed, the broadcaster must send a group 0A, 0B, or 15B with both TP and TA set to one to set a flag in a receiver indicating that the station is now transmitting a traffic report, and send a similar message with TP/TA set to 0 to turn off the flag.
In order for a receiver to scan the band to find a station broadcasting a traffic report, the data indicating a traffic report would need to be available in every B-Block being transmitted. Otherwise, if the moment a receiver tuned to a specific station and did not find the desired data, it would have to interpret the absence of that data as an indication that no traffic report is present, and go on to the next station. Otherwise, the receiver would be required to spend an indeterminable amount of time monitoring each and every station in a scan, rendering such a scan useless. Since the combination of TP/TA only appear in three group types (0A, 0B, 15B), and since a radio station for a variety of reasons might send other group types around the time of a traffic report, in the current situation receivers cannot be practically designed to use RDS/RBDS to scan to find radio stations broadcasting traffic reports.
Summarizing this concept with the previously discussed concept, RDS as currently structured does not promote an environment in which receivers can scan to find radio stations in a way that will satisfy the interests of either the listener or the broadcaster.
A third deficiency relates to the capabilities of Radio Text. Radio Text is implemented in application groups 2A and 2B. The Radio Text feature of Group Type 2A transmits a text stream of 64-characters; the Group Type 2B version of Radio Text transmits a 32-character text stream. The data transmitted by either version is a monolithic chunk, meaning the receiver treats it as a single chunk of 32-characters, or a single chunk of 64-characters. In addition, the protocol allows no identification as to what the data being carried represents. In other words, the data could be a string of asterisks, a message like xe2x80x9cWelcome to WQXR New York""s Classical Radio Stationxe2x80x9d, a phone number, or any other piece of information. The receiving radio has no way to tell the nature of this data or how to use it. The data can be displayed, and nothing else. Many receivers suppress the display of Radio Text data since in most cases the display screen on the radio is too small and therefore the Radio Text data must be scrolled across it, and since in the present state of the art the information to be transmitted is usually frivolous.
The present invention provides an enhanced radio data system which represents a significant improvement over RDS. As used herein, the term xe2x80x9cEnhanced Radio Data Systemxe2x80x9d is meant to indicate enhancements over both RDS and RBDS. The term xe2x80x9cRDSxe2x80x9d is used herein in a generic fashion to mean both RDS and RBDS transmission standards and receivers. Where there might be a difference between the U.S. and European standards, the term xe2x80x9cRBDSxe2x80x9d is used to refer specifically to the U.S. standard.
Among other things, the enhanced radio data system incorporates a protocol enhancement of RDS involving the redefinition of several bits within the B-block as illustrated in FIG. 3. This new protocol, which is backward compatible with RDS receivers, enables the efficient transmission of data such as xe2x80x9cArtist and Title,xe2x80x9d xe2x80x9cComing Next,xe2x80x9d DJ names, advertisements, phone numbers, etc., coupled with the ability of the receiver to handle this data in an intelligent way.
More specifically, the present invention offers several improvements over RDS, as set out in the following three items.
1. Improvements over Radio Text are afforded by a) providing the ability to transmit and display a large variety of messages within the limited bandwidth made available by the RDS data rate, especially messages relevant to the radio station and its broadcast; b) the specification of an expanded minimum screen size supports larger and more meaningful messages without scrolling, and the standardized positioning of information elements on this screen makes information understandable without additional explanatory information. Particularly, the Enhanced Radio Data System specifies a minimum screen size of two lines by 16 characters each, wherein, for Artist and Title information, xe2x80x9cArtistxe2x80x9d information would be presented on the top line and xe2x80x9cTitlexe2x80x9d would be presented on the bottom line, and wherein for Coming Next information, the words xe2x80x9cComing Next . . . xe2x80x9d would be presented on the top line, and the name of the event that is coming next would be on the bottom line, as illustrated in FIG. 4.
2. The present invention creates a sub-group applications in an encoding scheme that uses the Variable bits in the B-block to supply meanings to the data being transmitted, resulting in a) compression of the data by eliminating the need to transmit data to identify the nature of the data being transmittedxe2x80x94e.g., the application defines the Artist field, so only the name of the artist need be sent instead of a message like xe2x80x9cArtist=Elvis Presleyxe2x80x9d; b) compression of the data by eliminating the need to transmit characters, words and phrases that are implicit in the meaning of the data, and can be displayed by the receiver without having been transmitted (such as xe2x80x9cComing Next . . . xe2x80x9d); c) in computer terminology, the encoding scheme has the characteristic of xe2x80x9cfielded dataxe2x80x9d, having the advantage that the nature of the data is known to the receiver, which can then offer enhanced capabilities in acting upon a particular data element such as dialing a phone with a received phone number, or by populating the display with xe2x80x9cComing Next . . . xe2x80x9d as in the previous example; and d) since the data is fielded and the receiver knows the nature of the data, additional compression can be achieved by utilizing computer-style data compression techniques such as encoding telephone numbers in Binary Coded Decimal (BCD) format.
3. Radio stations can transmit indicators of announcements, such as News, Weather, Sports, or Traffic, independently of the Program Type specified in the B-block, and thus receivers can be designed to scan for stations broadcasting these announcements, while still being able to scan to find radio stations by program format.
Broadly stated, from an end-to-end system perspective the invention provides for an Enhanced Radio Data System comprising the same transmission and receiver elements as today""s RDS and RBDS. These transmission and receiver elements comprise: (i) a generating means for generating a carrier wave at a first predetermined frequency and a subcarrier wave at a second predetermined frequency; (ii) an encoding means for coding the text; (iii) a first modulation means for encoding the subcarrier with the text data generating an encoded subcarrier; (iv) a scheduling means for scheduling the encoding of the subcarrier wave at predetermined intervals; (v) a summing means for adding the audio signal and encoded subcarrier thereby generating a summed signal; (vi) a second modulation means for encoding the carrier wave with the summed signal thereby generating a modulated carrier wave containing both audio signal and text data; (vii) a transmission means for transmitting the modulated carrier wave; (viii) a receiving means for receiving the modulated carrier wave; (ix) a decoding means for decoding the audio signal and the text from the modulated carrier wave; (x) storage means for storing decoded text; (xi) a display means for displaying the text messages; and (xii) an audio signal playing means.
The invention also provides a method for encoding text messages into a commercial radio transmission comprising the steps of: (i) storing into memory a text message; (ii) generating a subcarrier of the carrier frequency of the radio transmission; (iii) segmenting the text message into text segments and blocks of binary data; (iv) assembling the blocks into groups of four blocks each, the groups comprising a data stream for transmission; (v) encoding the groups with Announcement Type bits and Sub-Group Application bits along with the associated data; (vi) modulating the subcarrier with the data stream; and (vii) transmitting the modulated subcarrier as part of the carrier frequency.
Like RDS receivers, the Enhanced Radio Data System receiver comprises an FM receiver, RDS demodulator and decoder, display, microprocessor and memory.